1. Field of the Invention
This invention relates to a tool post assembly for a machine tool, more particularly to a tool post assembly for quick displacement of a tool of a machine tool.
2. Description of the Related Art
Referring to FIG. 1, a conventional machine tool generally has a tool holding device 10 mounted thereon. The tool holding device 10 is shown to include a saddle 11 secured on an apron 20, a cross-slide 12 slidably mounted on the saddle 11 and having a cross-slide feedscrew 13 to perform an X-direction movement, a top-slide 14 slidably mounted on the cross-slide 12 and having a top-slide feedscrew 15 to perform a Y-direction movement, and a tool post 16 slidably mounted on the top-slide 14 and having a toolpost feedscrew 17 to perform a Z-direction movement. A tool 21 is selectively mounted in the tool post 16 so as to be operated by the tool holding device 10. However, in a precision processing operation, for example, a prober testing process for semiconductor chips or micromechanical devices, it is required to quickly remove the tool 21 away from a workpiece (not shown) to replace the workpiece or the tool 21 during the testing process. With such conventional tool holding device 10, the displacement of the tool 21 is quite slow so that the machining or precision processing efficiency is unsatisfactory.